Field
The present invention relates to devices, systems and methods for quantifying, analyzing and/or identifying chemical species. More specifically, the present invention relates to devices, systems and methods for analyzing chemical species through mass spectrometry or ion mobility spectrometry.
Description of the Related Art
Components of liquid samples are traditionally converted to gaseous ions by either a single step process or a two-step process. Representative examples of a single step system include both desorption ionization and spray ionization methods. Briefly, spray ionization entails a continuous flow of sample which is nebulized by either electrostatic nebulization or pneumatic nebulization (or alternatively, a combination of both electrostatic and pneumatic nebulization). The resulting electrically charged droplets are converted to gaseous ions through solvent evaporation. A representative example of a two-step process is conventional evaporation (i.e., thermodynamically controlled, slow evaporation) followed by gas-phase ionization. Gas-phase ionization is a necessary part of the two-step process because conventional evaporation does not result in the generation of gaseous molecular ions because it is simply too slow. Each of these methods has inherent limitations and/or disadvantages. Conventional evaporation followed by gas-phase ionization has the obvious disadvantage that not all potential analyte molecules can be evaporated: many species of analyte molecules (with a special emphasis on biomolecules) cannot be transferred to a gas phase without subsequent decomposition. Desorption ionization usually requires the drying of liquid samples and therefore cannot be directly used for real-time analysis of continuous sample flow. Spray ionization is currently the most viable method of converting liquid samples into gaseous ions. However, even this method suffers from several limitations, including: its inability to effectively convert fluid samples containing solid, floating material; its inability to accept a wide array of sample liquid viscosities; its inability to accept high concentrations of organic or inorganic salts in fluid samples (such as phosphate buffers or sodium chloride); and lastly its inability to effectively deal with high chemical complexity fluid samples.
Accordingly, there is a need for improved devices, systems and methods for converting liquid samples into gaseous ions.